BIOLOGY Q&A
More like study notes (by Evangelist)
a) i) Define the term genetics
the study of heredity(inheritance) and variation or study of mechanisms by which characteristics
are passed from parents to offspring
ii) List some characteristics which are inherited
size
height/length
colour/type
shape
yield
iii)State the importance of genetics
☆helps to explain differences between organisms of the same species
☆helps to explain the transmission of characters from generation‘ to generation
☆improvement in livestock
☆improvement in crops
☆can be used to treat some difficult diseases
b) i) Explain the meaning of the following terms
Heredity
☆the resemblance among individuals related by descent
☆transmission of traits from parents to offspring
Trait
☆also called character
☆A character of the organism e.g. type of ear, colour of eyes, height, yield etc.
Gene
☆unit of inheritance
☆it is the heredity factor which transmits traits from parents to offspring
☆genes are located at ‘fixed points on chromosomes
☆each point is called a locus (loci)
Allele
☆genes can exist in a series of alternative forms at a particular locus
☆allele refers to alternative forms of genes controlling a particular characteristic
Chromosomes
☆threadlike structures found in nuclei of all plants and animals
☆they carry genes which are hereditary materials
☆they consist of substances called DNA and proteins called histosones
DNA
☆deoxyribonucleic acid
☆substances that make up chromosomes
☆double helix(strand) molecule that contains genes
☆DNA consists of nucleotides
☆A nucleotide consists of an inorganic phosphate, ribose sugar and a base
☆There are four bases in a DNA molecule i.e. Adenine(A), guanine(G), thymine(T) and
cystosine (C)
☆Ribose sugar has four bases attached to it i.e. adenine, cystosine, guanine and thymine
☆Adenine pairs with thymine while guanine pairs with cystosine
☆Nucleotide initiates and controls protein synthesis
ii) List the types of chromosomes
☆somatic (body) chromosomes also called autosomes
☆sex chromosomes (related to reproduction)
c) i) What is variation?
☆sequence of differences occurring among individuals of the same species
ii) State the causes of variation in organisms
☆random assortment of genes during meiosis
☆crossing over
☆fertilization
☆doubling of chromosome numbers(mutation)
☆environmental conditions
iii) Name the types of variation
☆Continuous variation (differences not clear cut) e. g. height, length, weight, skin colour,
intelligence etc. They are quantitative and show intermediates
☆Discontinuous variation(differences are clear cut) e. g. ability to roll tongue, ABO blood
grouping system, RH factor, patterns of fingerprints, and ability to taste PTC. They are
qualitative and have no intermediates
iv) Explain the following terms
Acquired characteristics
☆they are as a result of adaptations due to the environment and are not inherited Inherited
characteristics
☆are passed down to offspring during sexual reproduction
Genotype
☆genetic constitution of an individual/genetic makeup
Phenotype
☆characteristics of an individual observed or discernible by other means i.e. observable
character
Dominant gene (character)
☆expressed in the phenotype when homozygous or heterozygous
Recessive gene
☆only expressed in homozygous state
Homozygous
☆when two alleles are identical e.g. LL,ll
Heterozygous
☆when two alleles are different at a particular locus e.g. Ll
F1 and F2
☆Fl means first filial generation i.e. the first generation produced when two varieties can be
crossed
☆F2 means second generation i.e. product of offspring or from F1 generation
d) i) Explain Mendels first law of inheritance
☆also called law of segregation
☆it states that genes are responsible for the development of individual characters
☆these characters are transmitted individually without any alterations
☆Only one character from a contrasting pair can be carried in a gamete, hence only one
character can be inherited.
ii) Give an example of this law
In an experiment, Drosophila (fruit fly) with long wings were crossed with those having
short wings. Assume letter L denotes gene for wing size. The gene for long wings is
dominant to that for short wings
the genes for dominant are LL and for recessive ll.
State the expected results for the first cross
iii) What is monohybrid inheritance?
☆when inheritance of one character is studied one at a time e.g. wing size only
☆the F2 generation (when selfed) always gives a phenotypic ratio of 3:1 and a genotypic ratio of
1:2:1 in a complete dominance
i) What is complete dominance?
☆refers to where only one dominant character is expressed while the other character which is
recessive is not expressed in the heterozygous state e. g. the case of wing size above e) i) What is
meant by co dominance?
When genes produce independent effects when heterozygous/none of the genes is dominant over
the other/where two or more alleles does not show complete dominance/recessiveness due to the
failure of any allele to be dominate in a heterozygous condition.
ii) Give an example of co dominance
☆In a certain plant species, some individual plants may have only white, red or pink flowers. In
an experiment a plant with white flowers was crossed with a parent with red flowers. Show
results of Fl generation. Use letter R for red gene and W for white gene.
☆If the plants form F1 were selfed, work out the phenotype ratio for the F2 generation
Phenotypic ratio 1 red:2 pink: 1 white
Genotypic ratio 1:2:1
f) i) What is a test cross?
☆A cross between an individual showing a character for a dominant gene(that is homozygous or
heterozygous) with a homozygous recessive individual
OR
☆a cross between individual(organism) of unknown genotype with a homozygous recessive
individual
ii) State the importance of a test cross in genetics
☆helps in determining the genetic constitution/genotype of an organism
iii) What are multiple alleles?
☆a set of more than two alleles that may determine a character
example is blood group which can be determined by any two of three alleles i.e. A,B and O
iv) Explain the inheritance of ABO blood groups
☆in humans blood groups are determined by three alleles i.e. A,B and O
☆it is only possible to have two genes at a time
☆genes A and B are co-dominant while gene O is recessive to genes A and B
Give a worked example using parents with heterozygous blood groups Ao and BO
ii) Explain the inheritance of Rhesus factor (Rh) in human beings
☆in humans blood is either Rh positive or Rh negative
☆people who have Rh antigen are Rh(+ve) while those without Rh antigen in their blood are
Rh(-ve)
☆Rh(+ve) is due to a dominant gene while the recessive gene causes lack of Rh factor.
☆When a person who is homozygous dominant marries a person who is homozygous
recessive the result is as shown below
☆Let the gene for dominant Rh factor be R while gene for recessive be r
iii) How is sex determined in human beings .
☆there are two sex chromosomes in humans, x and y
☆males are xy and females are xx
☆in females all ova have x chromosome
☆in males 50% of sperms contain x chromosomes While 50% of sperms contain y
chromosome
☆when a sperm containing x chromosome fuses with an ovum this results into a girl
☆when a sperm containing y chromosome fuses with an ovum the result is a boy
an example is given below.
g) i) What does the term linkage mean?
☆These are genes which occur together on a chromosome and are passed to offspring without
being separated ii) Define the term sex-linked genes
☆genes carried in the sex chromosome that are transmitted along with genes that determine sex
iii) What is meant by the term sex linkage?
☆genes are located on the sex chromosome
☆they are transmitted along with those that determine sex
iv) Name the sex-linked traits in humans
☆colour blindness
☆haemophilia
☆Hairy ears. pinna, nose
☆Baldness
☆Duchene muscular dystrophy (DMD) muscular wasting
v) Give an example of a sex linked trait in humans on:
Y Chromosome
☆tuft of hair sprouting from pinna/baldness
X Chromosome
☆colour blindness/haemophilia
vi) In humans red-green colour blindness is caused by a recessive gene C, which is sex-
linked. A normal man married to a carrier Woman transmits the trait to his children.
Show the possible genotypes of the children.
☆Let C represent the gene for normal colour vision (dominant)
☆Let c represent the gene for colour blindness
☆Parental phenotype Norman man x carrier woman
iv) State the importance of sex linkage
☆possible to determine sex of day old chicks
v) Haemophilia is due to a recessive gene. The gene is sex-linked and located on the x
chromosome. The figure below shows sworn offspring from phenotypically normal parents
What are the parental genotypes?
XY and XhX
Work out the genotypes of the offspring
h) i) What is mutation?
☆sudden change in the structure of DNA at a particular locus/chromosome/ gene
ii) Describe how mutations arise
☆mutations arise due to alterations in normal number of chromosomes
☆change in a portion of a chromosome affecting one or more genes
☆by chromosomal aberration e.g.
dleltion/duplication/substitution/inversion/translocation/crossing over
☆caused by mutagenic agents e. g. radiation (x-rays, ultra violet light, gamma rays) and
chemicals e. g. mustard gas/colchicines
iii)State the factors that may cause mutation
☆these are chemicals and radiations
☆Radiations Effects
☆X-rays gene/chromosome alteration
☆Ultra violet rays structural distortion of DNA
☆Chemicals Effect
☆colchicines prevents spindle formation
☆Cyclamate chromosome aberrations
☆Mustard gas chromosomes aberrations
☆Nitrous acid adenine in DNA is deaminated so behaves like guanine
☆Acridone orange addition and removal of bases of DNA
☆Formaldehyde.
iv) State the characteristics of mutations
☆arise suddenly
☆are unpredictable
☆random
☆generally rare
☆may breed true
☆some are desirable while others are lethal
v) Explain chromosomal mutation
☆- Change in nature, structure or number of chromosomes
vi) Explain how the following types of chromosomal mutations occur
Duplication
☆a section of a chromosome is repeated/replicates
☆therefore genes are repeated
Inversion
☆occurs when chromatids break at 2 places and when rejoining the middle piece rotates and
joins in an inverted position
Deletion
☆portion of a chromosome is left out after it breaks off
☆alters number and sequence of genes
Translocation
☆occurs when a section of a chromatid breaks off and becomes attached to another chromatid of
another chromosome
Non-disjuntion
☆Failure of homologous chromosomes/sister chromatids to separate/segregate during meiosis
Polyploidy
☆where number of chromosomes double or triple
☆beneficial in plants due to the following
☆increased yields/hybrid vigour//heterosis
☆resistance to pests
☆early maturity
☆resistance to drought
☆resistance to diseases
vii) What are gene mutations?
☆an alteration in the structure of a gene
i) Explain how the following occur during gene mutation
Deletion
☆some bases/nucleotides of a gene are removed
Inversion
☆the order of some bases/nucleotides of a gene is reversed
Insertion
☆addition of a base between two existing bases
Substitution
☆a portion of a gene is replaced by a new portion
ii) Name the disorders in humans caused by gene mutation
albinism
☆sickle cell anaemia
☆achondroplasia/chondordystorphic dwarfism
☆haemophilia
☆colour blindness
☆phenylketonuria
I. State the practical applications of genetics
i. Breeding programmes (research)
☆high yielding/hybrid vigour/heterosis
☆resistance to diseases
☆resistance to drought/salinity
☆early maturing
ii. Genetic engineering
☆genetic manipulation to produce desired characteristics
iii. Law
☆- legal questions of paternity knowledge of blood groups or blood transfusion
iv) Genetic counseling
☆aimed at reducing harmful traits e.g. albinism, congenital idiots, colour blindness e.t.c
v) Others
☆- Pre-sex determination
☆Understanding human evolution and origin of other species.
2. a) i) Explain the meaning of evolution
☆a gradual change in living organisms from simple life forms to more complex forms over a
long period of time.
ii) Differentiate organic evolution from chemical evolution as theories of origin of life
☆organic evolution refers to the emergence of present forms of organisms gradually from pre-
existing forms (some of which no longer exist)
☆chemical evolution explains the origin of life as having occurred when simple chemical
compounds reacted to form the simplest life forms
iii) What is special creation?
☆maintains that the whole universe and all living organisms came into being due to the act of a
supernatural being
b) Discuss the various kinds of evidence for evolution
i) Fossils
☆fossils are remains of organisms preserved in naturally occurring materials for many years
☆they give evidence of types of plants/animals that existed at certain geological age/long
ago/millions of years ago
☆gives evidence of morphological/anatomical/structural changes that have taken place over a
long period of time e. g. human skull, leg of horse
ii) Comparative anatomy
☆gives evidence of relationship among organisms/gives evidence of a common ancestry of a
group of organisms
☆organisms have similar structures/organs performing the same function e. g. digestive system]
urinary system/nervous system/vestigial structures and vertebrate heart
☆Divergence where the basic structural form is modified to serve different functions e.g.
vertebrate forelimb/beak structure in birds/birds feet/parts of a flower. These are called
homologous structures
☆homologous structures have a common embryonic origin but are modified to perform different
functions e.g. the pentadactyl .
☆adaptive radiation is a situation where organism have a homologous structure with common
embryonic origin which is modified to perform different functions to adapt organisms to
different ecological niches/habitats e.g. beaks of Darwinian finches(birds)
☆Convergence is where different structures are modified to perform a similar function e.g.
wings of birds and insects/eyes of humans and octopuses. These are called analogous structures
☆Vestigial structures are greatly reduced in size and have ceased to function e.g. human
appendix/caecium/coccix in humans, wings of kiwi (flightless bird), presence of hind limb pad in
python, halters in insects, human hair nictitating membrane in human eye, human ear muscle,
pelvic girdle in whale and third digit of wing of bird.
iii) Comparative embryology
☆some embryos of different animals appear very similar thus showing relationship and
possibility of a common ancestry
e.g. different classes of vertebrates larvae of annelida and mollusca are similar (tocophere)
iii) Comparative serology/physiology
☆these show biochemical and immunological comparisons of blood groups/components to show
immunological similarities of tissues therefore showing relatedness of different organisms
e.g. antigen antibody reactions, human blood groups/Rh factor reveal some phylogenic
relationship among organisms/common ancestry
iv) Geographical distribution
☆organisms differ in various geographical regions
☆present continents are thought to have been a large land mass joined
☆together/pangea/Eurasia/Gondwanaland
☆present continents drifted apart from one land mass/continental drift
☆as a result of continental drift isolation of organisms occurred bring about different patterns of
evolution
☆organisms in each continent evolved along different lines hence emergence of new
species/divergence/convergence.
Examples
☆marsupials in Australia
☆llama, jaguar, panther in S. America
☆lion, camel in Africa
☆I tiger in Asia
vi) Cell biology (cytology)
☆structures and functioning of cells are similar
☆occurrence of organelles e.g. mitochondria in all cells/both plant and animal cells
☆these point at a common ancestry.
c) i) State the evolutionary characteristics that adopt human beings to the environment
☆- Brain
☆- Eyes
☆- Upright posture/bipedal locomotion
☆- prehensible arm/hand
☆- Speech
ii) State the ways in which Homo sapiens differs from Homo habilis
☆standing upright/erect posture
☆intellectual capacity/higher thinking capacity/bigger brain/higher brain capacity
☆communication through language/speech
d) i) Explain Larmarck’s theory of evolution
☆- Inheritance of acquired characteristics/environment induces production of a favorable trait
which is then inherited
ii) Explain why Lamarck’s theory of evolution is not accepted by biologists today
☆- evidence does not support Lamarck’s theory
☆- acquired characteristics are not inherited/inherited characteristics are found in reproductive
cells only
iii) Explain Darwin’s theory of evolution
☆- inheritance of genetically acquired characteristics
☆- a character happens to appear spontaneously which gives advantage to an organism therefore
adapted then inherited through natural selection
e) i) What is natural selection?
☆- Organisms with certain characteristics are favoured by the environment
☆Such organisms tend to survive and produce viable offspring
☆Others not favored are eliminated from subsequent generations
ii) With examples, explain how natural selection takes place
☆- organism with certain characteristics are favored by their environment
☆- such organisms tend to survive and produce viable offspring
☆- others not favored are eliminated from subsequent generations
☆- as the environmental conditions change the survival value of a character may alter with time
so that characteristics which were favored may no longer have advantage and other characters
may then become favorable
- if a favorable character is inherited, then offspring produce generations which are better
adapted to survive in a population
☆- more offspring are produced than can survive which results in struggle for survival - the
fittest survive.
iii) State the advantages of natural selection to organisms
☆- assist to eliminate disadvantageous characteristics/perpetuates advantageous characteristics
☆- allows better adapted organisms to survive adverse changes in the environment/less adapted
organisms are eliminated
iv) State the ways in which sexual reproduction is important in the evolution of plants and
animals
☆- brings about useful variations/desirable characters
☆- variations make offspring better adapted for survival/more resistant to diseases
☆- may lead to origin of new species
v) Explain the significance of mutation in evolution
☆- Mutation bring about variation which can be inherited
☆- Some of these variations are advantageous to the organism
☆- Others are disadvantageous
☆- The advantageous variations favour the organism to compete better in the struggle for
survival
☆- This results into a more adapted organism to its environment or new species/varieties
☆- Those with disadvantageous characters will be discriminated against therefore eliminated
from the population/death/perish
vi) Plain why it is only mutations in genes of gametes that influence evolution
☆- gametes form the new offspring
vii) How would you prove that evolution is still taking place?
☆- resistance of organism to antibiotics, pesticides and drugs
☆- new varieties of bacteria are resistant to certain antibiotics such as penicillin
☆- houseflies and mosquitoes are resistant to DDT
vii) Explain why some bacteria develop resistance to a drug after they have bee subjected
to it for some time
☆- bacteria mutates/develops a new strain/chemical composition is altered hence is able to
produce enzymes/chemicals which degrade the drug rendering it non-susceptible to the drug
☆- the new strain is favoured by selection pressure natural selection
f) How has industrial melaninism i.e. peppered moth contributed towards the mechanism
of evolution
☆- This is an example of natural selection
☆- The peppered moth exists in two distinct forms, the speckled white form (normal form) and a
melanic form (the black/dark)
☆- They usually rest on leaves and barks of trees that offer camouflage for protection
☆- Originally the “speckled white” form predominated the unpolluted area of England
☆- This colouration offered protection against predatory birds
☆- Due to industrial pollution tree barks have blackened with soot
☆- The white form underwent mutation
☆- A black variety/mutant emerged suddenly by mutation
☆- It had selective advantage over the white forms that were predated upon in the industrial
areas
☆- The speckled white form is abundant in areas without soot/smoke.
3. a) i) Define irritability, stimulus and response irritability
☆-also called sensitivity
☆- Responsiveness to change in environment
Stimulus
☆A change in the environment of organism which causes change in organism’s activity
Response
☆- change in activity of an organism caused by a stimulus
ii) State importance of irritability to living organisms
☆- Adjusting to environmental conditions. Sensitive/defect/responding
iii) List the examples of external stimuli to organisms
☆- air/oxygen (aero)
☆- light(photo)
☆- osmotic pressure (osmo)
☆- current (Rheo)
☆- chemical concentration (chemo)
☆- \water/moisture (hydro)
☆- Touch/contact (hapto/thigmo)
☆- Gravity/soil (geo)
☆- Temperature (thermo)
b) i) What are tactic responses?
☆- response in which whole organism or its motile parts move e. g. gamete
ii) What causes tactic responses?
☆- caused by unidirectional stimulus
☆- usually doesn’t involve growth
☆- response is either positive or negative
☆- named according to source of stimulus
- e.g phototaxis, aerotaxis, chemotaxis
iii) State the importance of tactic response to:
Members of kingdom protista
☆- move towards favorable environment/move away from unfavorable environment
☆- move towards their prey/food
Microscopic plants
☆- escape injurious stimuli/seek favorable habitats
iv) Name the type of response exhibited by:
☆Euglena when they swim towards the source of light
☆- phototaxis
☆- sperms when they swim towards the ovum
☆- chemotaxis.
v) State the advantages of tactic responses to organisms
☆- to avoid unfavorable environment/injurious stimuli
☆- escape from predators
☆- to seek favorable environment
☆- to seek for food/prey
c) i) Define the term tropism
☆- growth movement of plants in response to external unilateral/unidirectional stimuli
ii) Explain the various types of tropism in plants
Phototropism
☆- growth movements of plant shoots in response to unilateral sources of light
☆- the tip of the shoots produce auxins down the shoot
☆- light causes auxins to migrate to outer side/darker side causing growth on the side away from
light hence growth curvature towards source of light roots are negatively phototrophic
Geotropism
☆- response of roots/pans of a plant to the direction of force of gravity
☆- auxins grow towards the direction of force of gravity causing positive geotropism in roots
while shoot grows away from force of gravity (negatively geotrophic)
Thimotropism/Haptotropism
☆- growth response of plant when in contact with an object
☆- contact with support causes migration of auxins to outer side causing faster growth on the
side away from contact surface
☆- this causes tendrils/stem to twin around a support
Hydrotropism
☆- growth movement of roots in response to unilateral source of water/moisture
☆- the root grows towards the source of water/ positively hydrotropic while leaves are negatively
hydrotropic
chemostropism
☆- growth movement of parts of plant to unilateral source of chemicals
☆- the chemicals form a gradient between two regions e.g. pollen tube growing towards the
ovary through the style
iii) State the ways in which tropisms are important to plants
☆- expose leaves/shoots in positions for maximum absorption of sunlight for photosynthesis
☆- enables roots of plants to seek/look/search for water
☆- enables plant stems/tendrils to obtain mechanical support especially those that lack woody
stems.
☆- enables roots to grow deep into the soil for anchorage
☆- enables pollen tube grow to embryo sac to facilitate fertilization
iv) Explain the differences between tropic and tactic responses
Tropism
☆-growth curvature in response
☆-slow
☆-influenced by hormones
Taxes
☆-locomotory response
☆-fast
☆-external influence
d) The diagram below represents growing seedlings which were subjected to unilateral
light at the beginning of an experiment
i) State the results of P, Q and R after S days
- P will bend/grow towards light
- Q will remain straight/have little or no growth
- R will
remain/grow
straight/grow upwards
ii) Account for your
results in (i) above
☆P- Growth substance/growth hormone/IAA/auxin are produced by the stem tip
☆ they move (downwards and get distributed) to the side away from light where they cause
rapid/more growth/cell division/elongation that results in bending
Q- Source of auxin has been removed
R- The auxins cannot be affected by light because the tip has been covered
iii) If the tin foil were removed from the tip of seedling R, what results would be observed
after two days
- it will bend/grow towards light
iv) State the expected results after 3 day is if the box were removed
☆- all seedlings will grow straight/upwards
e) In an experiment to investigate a certain aspect of plant response, a seedling was placed
horizontally as shown in diagram I below. After seven days the appearance of the seedling
was as shown in diagram 2
Account for the curvature of the shoot and root after the seven days
i) Shoot
☆- auxins accumulate on the lower side of the seedling due to gravity
☆- high concentration of auxins in shoot stimulates faster growth causing more elongation on the
lower side than the upper side hence curvature occurs upwards
ii) Root
☆- the high concentration of auxins inhibits growth hence the upper side with less auxins grows
faster than the lower side therefore the curvature occurs downwards
f) What is etiolation?
☆- phenomenon exhibited by plants when grown in darkness
☆- such plants are pale yellow due to absence of chlorophyll, have small leaves, long
stems/hypocotyle and slender stems
☆- plants exhibit etiolation to reach light/obtain light
☆- this is a survival response.
4. a) i) What is coordination in animals
☆- The linking together of all physiological activities that occur in the body so that they take
place at the night time and in the correct place
ii) Name the main systems for coordination in animals
☆- Nervous system/sensory system
☆- Endocrine (hormonal system)
iii) List the components of the mammalian sensory system
☆- Central nervous system (CNS), brain & spinal cord
☆- Peripheral nervous system (PNS) cranial and spinal nerves
☆- Sense organs
☆- Autonomic nervous system (ANS) nerve fibers and ganglia
iv).Explain the terms receptors, conductors and effectors
☆- Receptors are structures that detect stimuli i.e. sense organs
☆- Conductors transmit impulses from receptors to effectors e. g. neurons
☆- Effectors are the responding parts e.g. muscles, glands
v) What are the functions of the central nervous system?
☆- provides a fast means of communication between receptors and effectors
☆- coordinates the activities of the body
vi)
State the
differences between somatic and autonomic systems of peripheral nervous system
☆- Somatic is concerned with controlling the conscious or voluntary actions of the body i.e. skin,
bones, joints and skeletal muscles
☆ the autonomic (automatic) nervous system controls involuntary actions of internal organs,
digestive system, blood vessels, cardiac muscles and glandular products.
b) i) What is a neurone?
☆the basic unit of the nervous system
☆also called nerve cell
☆conducts impulses
☆include monitor sensory and relay neurons
ii) Name the parts of a typical neurone and state the functions of each part
☆cell body/centron contains nucleus and cytoplasm
☆axon transmits impulses away from cell body
☆dendrites relays impulses across adjacent neurons
☆myelin sheath insulates axon and speeds up transmission of impulses
☆schwan cells forms myelin sheath and aid in nutrition and regeneration of axon
☆node of ranvier occur between schwan cells, where axon is not covered, speeds up impulse
transmission
☆nissils granules contain mitochondria that provide cell body with energy for metabolic process.
i) Describe the structure and function of a motor neurone
☆motor neurone relays impulses from CNS (brain/spinal cord) to effectors ( muscles/glands)
ii) Describe the structure and of sensory neurone
☆sensory neurone relays receptors (sense organs) to CNS
iii) State structural differences between motor and sensory neurons
☆Cell body in motor neurone is terminal (at the end) and inside central nervous system.
☆Cell body in sensory neurone is terminal but has axon at both ends (bipolar)
iv) Describe the structure and function of a relay neurone
☆also called intermediate/internucial/associate/connector/interneurone
☆locate inside central nervous system and spinal code
☆usually lack myelin sheath
c)
State the function of the major parts of the human brain.
i) Cerebrum
☆called forebrain
☆occupies most of the brain
☆consists of four lobes each with specific function
☆temporal lobe controls taste smell hearing learning and memory
☆partial lobe controls sensory output and touch
☆occipital lobe controls vision, motor output and speech
☆frontal lobe controls personality, learning thought and speech
☆also has parts called thalamus and hypothalamus
☆thalamus helps to sort sensory information
☆hypothalamus controls hunger, heartbeat body temperature and aggression
ii) Mid brain
☆quite small in humans
☆relay centre for audio and visual information
☆also involves in some sight, hearing and orientation responses
i) Hind brain
☆consists of cellebral and medulla oblongata
☆cerebellum is responsible for coordinating impulses, posture and balance, motor ☆coordination
and muscle tone
☆medulla oblongata controls heartbeat, blood pressure breathing rate, coughing and sneezing.
a) i) What is reflex action?
an automatic response to an external stimulus e. g. sneezing or Withdrawing hand from a hot
object
ii) Describe a reflex action that will lead to the Withdrawal of a hand from a hot object
☆Receptors in the skin respond to stimuli. Arestimulated
☆an impulse is transmitted through the sensory neurone, across a synapse to the ☆central
nervous system (White matter), through the relay neurone into grey matter, then to the motor
neurone and finally to the effect muscle which contracts
the hand is then withdrawn.
iii) Explain how an impulse is transmitted across the synapse (gap)
☆impulse initiates release of transmitter substance acetylcholine at the end of the sensory
neurone
☆acetylcholine diffuses across the synapse and generates an impulse in the next neurone
ii) Briefly describe the transmission of a nervous impulse across a neuro-muscular junction
☆impulse arrives at synoptic knob and causes vesicle to move to the pre-synaptic membrane
☆vesicle discharges transmitter substance into synaptic cleft
☆transmitter substance/acetylcholine diffuses across the cleft and attaches to post-synaptic
membrane
☆the membrane is depolarized, generating the action potential
iii) What are the functions of a synapse?
☆allows transmission of nerve impulses from neurone to neurone
☆ensures nerve impulses travel in only one direction W
☆in the brain they store information/memory
b) i) What is a conditioned reflex?
☆A response caused by a unilateral stimulus (associated stimulus) which substitutes the normal
stimulus.
ii) Explain a conditioned reflex
☆it is automatic
☆it involves the spinal cord
☆it is usually learned e. g. writing, cycling, dancing
☆it involves the interaction of highly specialized centers of the brain with a large number of
neurone necessary to bring about conditioning
☆example is experiments carried out by Pavlov using dogs
iii) Compare a simple reflex action with a conditioned reflex.
c) i) What
are
endocrine glands?
☆ductless glands that produce hormones in animals
☆hormones are chemical substances which help to coordinate the functions of the body
ii) State the functions of hormones in animals
☆regulate growth and development
☆control behavior during breeding
☆proper functioning of cells
☆regulate metabolic activities
iii) Name the main endocrine glands, their secretions and functions in the human body
Gland: Thyroid
Hormone:
Thyroxine
Function:
☆increases the rate of metabolism
Gland: Parathyroid
Hormone:
☆Parathyroid hormone
Function:
☆regulates calcium and phosphate levels
Gland: Pituitary
Hormone:
growth hormone
Function:
☆regulates growth of the body
gonadotrophic hormone
Function:
☆stimulates the growth of male and female organs
lactogenic hormone (prolactine)
Function:
☆stimulates secretion of milk after child birth
Thyrotropic hormone( TSH)
Function:
proper functioning of thyroid glands/thyroxine production
Adrenocorthicotropic hormone (ACTH)
Function:
☆stimulate release of adrenal cortex hormone
oxytocine hormone
Function:
☆regulates blood pressure
☆stimulates smooth muscles
☆stimulates contraction of uterus during child birth
☆aids flow of milk from mammary glands.
Follicle stimulating hormone (FSH)
Function:
☆causes maturition of egg in females
☆stimulates sperm production in male
Vasopressin (ADH) antidiuretic hormone
Function:
☆regulates water balance by kidney
Gland: adrenal
Adrenaline (epinephrine hormone)
Function:
☆for emergency
☆prepares body to cope up with stress
Aldosterone hormone
Function:
☆maintain balance of salt and water in blood
Corrtisone hormone
Function:
☆break down the stored proteins to amino acids
☆aids in the break down of adipose tissue
☆regulates sugar levels in the blood
☆prevents inflammation
Sex hormone
Function:
☆supplements sex hormones produced by gonads
☆promotes development of sexual characteristics
Gland: Pancreas
Hormone:
Insulin
Function:
☆regulates levels of sugar in blood
☆enables liver to store sugars
glucagon
Function:
☆regulates levels of sugar in blood
Gland: ovaries
Hormone:
Oestrogen Function:
☆causes secondary sexual characteristics in female
☆prepares the uterus for pregnancy
progesterone Function:
☆growth of mucus lining of uterus
☆maintains the uterus during pregnancy
Gland:testes
Hormone:
☆androgen testosterone
Function:
☆causes secondary sexual characteristics in male
Gland: stomach cells
Hormone:
Gastrin
Function:
☆stimulates release of gastric juice.
iv) Give the differences between nervous and endocrine (hormonal) communication
nervous
☆response confined to effector organs( localized target)
☆speed of response is rapid
☆nervous impulse through nerve/nerve cells/neurons
☆duration of response is short
☆speed of transmission is rapid
☆transmission is electrical
hormonal(endocrine)
☆response more widespread (various targets)
☆response less rapid
☆hormones transferred through blood
☆persistent for long
☆speed of transmission is slower
☆transmission is chemical
v) State the effects of over secretion and under secretion of adrenaline and thyroxine in
hum
ans.
g) i) Define the following terms
Drug
☆a substance that causes a change in body function
Drug abuse
☆indiscriminate use of drugs without minding their side effects
☆misuse or wrong use of drugs
ii) State the types of drugs, examples and side effects
Sedatives
☆also called depressant
☆a drug that decreases the action of the central nervous system
☆reduce anxiety, and tension, induce sleep and act as muscle relaxants
☆when abused they cause withdrawal effects such as anxiety, delirium and death
☆includes barbiturates, other sedatives, tranquilizers and alcohol
Pain-killers
☆suppress centers of pain in the brain
Hallucinogens
☆given to people with hallucination or mentally ill patients to calm then down
☆when abused they lead to a feeling of confusion, agitation, depression and violent behavior that
can lead to murder or suicide
☆examples include valium, LSD, bhang, narcotics and cannabis
Stimulants
☆drugs that temporarily increase the action of the central nervous system
☆they create a feeling of alertness, wakefulness, a sense of self confidence and well being
☆used to decrease fatigue and mild depression
☆when abused they cause feelings of persecution, hallucination and addiction
☆include amphetamines, cocaine, caffeine, miraa and nicotine.
iii) State the general effects of drug abuse on human health
☆damage to body organs e. g. liver cirrhosis
drug addiction
☆impaired judgment resulting in clumsiness
☆socio-economic problems e. g. crime, loss of jobs, divorce, prostitution, HIV/AIDS
☆may cause poor health
h) i) List the special sense organs in mammals and the major function of each
☆- Eye for sight
☆- Ear for hearing and balance
☆- Nose for smell
☆ Skin for touch, temperature detection, pain detection.
5. a) i) What is support?
☆to support is to carry part of the weight/mass of an organism
ii) What is locomotion?
☆progressive change in the position of an organism
iii) State the importance of support systems in living organisms
☆they provide a framework for the body of organisms and help to determine their shape
☆provide land animals with means for support to their weights against gravity
☆organs are attached to the skeleton for support and stability to avoid entanglement and crushing
each other
☆they protect very important and delicate organs whether inside or outside the body e. g. eyes,
heart
☆in large plants the rigid trunks of trees support the greater mass of leaves and fruits
iv) State the importance of locomotion in animals
☆in search of food
☆Search for mates
☆escaping predators
b) i) Name the tissues in higher plants that provide mechanical support
☆Sclerenchyma
☆collenchyma (not lignified)
☆xylem/tracheids and vessels
ii) State the importance of support in plants
☆exposing the surface area of leaf to sunlight for photosynthesis
☆ensure flowers are exposed to pollination agents
☆expose fruits and seeds to agents of dispersal
☆to resist breakages due to their own weight and that of other organisms
☆for proper transport and translocation of materials
iii) Name the types of plant stems
☆herbaceous e.g. shrubs
☆woody e. g. trees
☆weak stems in creepers, twining plants and plants bearing tendrils
iv) Name the tissues in plants that are strengthened with lignin
☆sclerenchyma
☆xylem vessels/tracheids/xylem
v) What makes young herbaceous plants remain upright?
turgidity
☆presence of collenchyma.
vi) State the ways by which plants compensate for lack of ability to move from one place to
another
☆ability to pollinate
☆response to nastic and tropic movement
☆ability to exploit localized nutrients
☆ability to disperse seed or fruit propagation
c) i) Explain the Ways in which erect posture is maintained in a Weak herbaceous stem
☆ This is the function of turgidity and presence of collencyma
☆Cells take in water and become turgid
ii) Explain how support in plants is achieved
☆Turgor pressure due to absorption of water keeps cells firm hence hold herbaceous plants
upright
☆collenchyma and clerenchyma tissues are closely packed in stem and roots to provide support
☆inelastic cuticle on epidermis is covered by a waxy layer hence keeping shape of plant and
setting inward pressure against turgid cells and this causes a force to hold plant upright
☆xylem vessels and tracheids are lignified to provide support to stems, roots and leaves
☆climbing plants obtain mechanical support from other plants and objects
☆they have climbing structures like tendrils which hold on to other objects
d) i) Give the reasons why support is necessary in animals
☆for attachment of muscles
☆For attachment of other body organs
☆to protect delicate body organs
☆to maintain body shape/form
☆to enable movement/locomotion
ii) Why is movement necessary in animals?
☆enables animals to search for food
☆enables animals to search for shelter
☆enables animals to escape predators/harmful conditions
☆enables animals to Search for water
☆enables animals to search for mates
☆enables animals to search for breeding sites
e) i) Name the organ used for support by animals
- Skeleton
ii) Name the different types of skeletons in animals, giving an example of an animal for
each type of skeleton named
☆exoskeleton e.g. arthropoda (crab, insect)
☆endoskeleton e. g. chordata (cat, fish)
iii) State the difference between exoskeleton and endoskeleton
☆endoskeleton is a rigid framework covered by body tissues of an animal
☆exoskeleton is a rigid framework found on the surface of an animal.
iv) State the advantages of having an exoskeleton
☆supports/protects delicate inner parts
☆water proof/prevents drying up of body
☆provided surface for muscle attachment
v) Explain the importance of having an endoskeleton
☆support the body
☆give body its shape
☆protect delicate organs e. g. skull, brain, ribs
☆used in locomotion e.g. bones serve as levers
☆red blood cells are formed in bone marrow
☆minerals are stored in bones e. g. calcium and phosphorus
f) i) Explain how a fish is adapted to living in Water
☆streamlined body for easy movement in water
☆swim bladder controls depth of swimming
☆fins for movement, balance, direction and stability,
☆gills for gaseous exchange in water
☆presence of lateral line to sense vibrations
☆scales provide protection .
☆colour which offers camouflage against predators
ii) Explain how a finned fish is adapted, to locomotion in Water
☆streamlined body to reduce resistance/friction )to swim smoothly)
☆the vertebral column consists of a series of vertebrae held together loosely so that it is flexible
☆myotomes/muscles associated with vertebral column produce movement
☆the sideways and backwards thrust of the tail and body against water results in resistance of
water pushing the fish sideways and forwards in a direction opposed to thrust
☆heat not flexible so as to maintain forward thrust
☆presence of fins help in propulsion/balance/paired fins (pectoral and pelvic) for controlling
pitch and slow down movement/unpaired fins (dorsal, ventral, anal) for yawing and rolling
(caudal) for swimming/propulsion and steering/change of direction
☆presence of swim bladder to make fish buoyant
☆scales tip towards the back to provide smooth surface
☆body covered with mucus to reduce friction
☆flattened surface for easy floating.
g) i) Name the main parts of the vertebral column giving the types of bones found in each
part
Axial skeleton
☆forms the main axis of the body
☆formed by the skull, sternum, ribs and vertebrae
Appendicular skeleton
☆composed of limbs and girdles
☆the forelimbs are connected to the trunk by the pectoral girdles (shoulder bones)
☆hind limbs are connected to the pelvic girdle (hips)
☆bones are scapular, clavicle, humerus, ulna, femur, tibia, fibula, metacarpals, carpals, tarsals,
metatarsals, phalanges, ilium, ischium and pubis
ii) What are the vertebrae?
☆bones of the vertebral column
iii) State the functions of the vertebral column
☆gives flexibility
☆absorbs shock
☆protects spinal cord
☆supports weight of body
☆provide surface for muscle attachment
☆between the vertebrae are soft discs which offer cushioning called interverterbral discs
iv) State the general characteristics of vertebrae
☆have solid structure called centrum to support weight of body
☆has transverse process lateral to centrum for muscle attachment
☆neural spine is dorsal to centrum and provides surface area for muscle attachment
☆neural canal a passage for spinal cord and offers protection to it
☆has facets for articulation with other vertebrae
☆neural arch encloses neural canal.
v) Name the bones of the vertebral column
☆- Cervical vertebra
☆— Thoracic vertebra
☆- Lumbar vertebra
☆- Sacral vertebra
☆Caudal vertebra
vi) Describe how the various vertebrae are adapted to their functionsm
Bones:
skull
Structure:
☆cranium and jaw bones
☆made of several bones joined together
☆large box called cranium and smaller paired boxes for eyes, ears, nose, jaw
☆has large hole called foramen magnum for passage of spinal cord
Function:
☆attachment of jaws
☆protect brain and other delicate parts
Bone:
☆cervical region Atlas (first cervical)
Structure:
☆ring shaped
☆no centrum
☆broad flat transverse processes
☆vertebraterial canal for passage of vertebra artery
☆facet for articulation of condyles of skull
Function:
☆protects the spinal cord
☆attachment of muscles
☆allow nodding of head
Bone:
☆axis (second cervical)
☆Structure:
☆adontoid peg projects from centrum
☆large flattened neural spine
☆vertebraterial canal
☆small transverse process
Function:
☆allows the head to rotate
☆protects the spinal cord
☆provides surface for muscle attachment
Bone:
☆cervical (others) Structure:
☆short neural spine
☆branched transverse process for neck muscles
☆vertebraterial canal
☆wide neural canal
Function:
☆supports weight of the head
☆protects the spinal cord
☆neck muscle attachment
Bone:
☆Thoracid
Structure:
☆long backwards pointing neural spine
☆transverse process that points sideways
☆facets for articulation of ribs
☆notch for spinal nerves to pass through
Function:
☆forms ribcage
☆articulation with one end of rib
☆protects the spinal cord
☆muscle attachment
Bone:
☆lumbar
Structure:
☆short neural spine
☆long transverse process towards abdomen
☆large centrum
☆extra processes e.g prezygapophysis, hypapophysis, anapophysis,metapophysis
Function:
☆protects organs of the abdomen
☆supports the upper part of the body
☆protects the spinal cord
☆muscle attachment
Bone:
sacral
Structure:
☆fused bones to form sacrum
☆well developed transverse processes of first vertebra
☆vertebraterial canal
☆short neural spine
Function:
☆protects the alimentary canal
☆attachment of hip girdle
☆protects the spinal cord
☆muscle attachment
Bone:
Rib
Structure:
☆long
☆flattened
☆attached to sternum from front
Function:
☆protects internal organs
☆muscle attachment
vii) Describe the bones that form the appendicular skeleton
Bone:
☆pectoral girdle (scapular shoulder bone)
Structure:
☆broad i,e flattened blade
☆glenoid cavity to articulate with humerous
☆metacronium/acromion for muscle attachment
☆hard to provide support
☆socket with cartilage/smooth surface to reduce friction
Function:
☆support muscle attachment
☆articulate with humerous
Bone:
Humerous
Structure:
☆long shaft for muscle attachment
☆round head to articulate with glenoid cavity
☆trachlea for articulation with ulna
☆olecranon fosa to prevent arm bending the other way
Function:
☆movement
☆muscle attachment
Bone:
Ulna and radius
Structure:
☆ulna longer and on side of little finger
☆has sigmoid notch and olecranon process to form hinge joint with humerous
☆radius is smaller and lies along thumb side and does not join ulna
☆allows articulation with wrist bone
Function:
☆movement
☆muscle attachment
Bone:
pelvic girdle (hip bone)
Structure:
☆composed of three fused bones ilium, ischium, pubis
☆upper end fused to sacrum
☆lower end has acetabalum for articulation with femur
☆has abturator
Function:
☆movement
☆muscle attachment
☆support
☆absorbs pressure exerted by ground when animals move
6. a) What is a joint?
☆the point where bones meet
ii) State the functions of joints
☆provide a point of articulation between bones
iii) Name the main types of joints
☆immovable joints e.g. skull, pelvic girdles and sacrum
☆slightly movable joints e. g. between vertebrae
☆Freely movable joints e. g. knee, elbow
iv) Give the features of movable joints
☆ends of bones covered with articular cartilage
☆ends bound by capsules of ligaments
☆have joint cavity filled with lubricating fluid called synovial fluid secreted by synovial
membrane
☆they are called synovial joints
b) Describe the synovial joints
iv) Ball and socket
☆allow movement in all planes /directions i.e. 360°
☆rounded end of bone fits into a rounded/cavity in another bone
e.g. shoulder joint and hip joint
v) Hinge joint
☆convex surface of one bone fits into the concave surface of another bone
☆this allows movement in only one plane/direction 180°
e.g. elbow joint and knee joint.
vi) Pivot joint
☆allows rotation e. g. where atlas pivots on olecranon process of axis
c) i) What is synovial fluid?
☆lubricating fluid produced by synovial membrane at movable joints
ii) State the functions of synovial fluid
☆absorbs shock
☆reduces friction/ gives lubrication
☆nourishment
☆distributes pressure
d) Explain the following terms
v) Ligament
☆connective tissue joining one bone to another
vi) Cartilage
☆supporting soft tissue found at joints
they cushion the bones and absorb shock
vii) Tendon
☆tissue that connects muscle to bones
7. Muscles
e) i) What is a muscle?
☆fleshy part of body
☆composed of long cells enclosed in a sheath
☆specialized cells capable of contracting
ii) State the functions of muscles
☆cover the skeleton
☆provide shape
☆contract and relax to enable body to move
f) Describe the structure and function of various types of muscles
i) skeletal muscles
☆also called voluntary/striated/stripped muscles
☆they are attached to skeleton
☆they consist of striated, multinucleated, ling fibers and are cylindrical shaped
☆found on legs, arms, eyes, neck where they cause movement
ii) Involuntary muscles
☆also called smooth/visceral/unstriated/unstripped
☆their movement is not controlled by the will
☆they are unstriated, nucleated, short fibred and spindle shaped
☆are found in alimentary canal, blood vessels, secretory glands, other tubular visceral
☆organs, bladder, uterus, urinary tract, reproductive system, respiratory tract, ciliary body iris
iii) Cardiac muscles
☆also called myocardium
☆found in the Walls of the heart
☆are not under control of the will
☆composed of long cylindrical cells with special junctions
☆myogenic i.e. generate their own contraction
☆they are not fatigued
☆their function is contraction of the heart to pump blood
g) Explain how muscles cause movement of the human arm
☆the muscles which bring about these movements are called biceps and triceps
☆biceps are attached to scapula and radius for bending
☆triceps are attached to scapula, humerus and ulna for stretching
☆when the biceps contracts, it pulls the radius (forearm) and the hand bends
☆the triceps relaxes at the same time
☆when the triceps contracts and biceps relaxes(extends) the arm is stretched
☆biceps flexes the arm (flexor) and triceps extend(extensor muscle) the arm
h) i) State the structural differences between skeletal muscles e.g. biceps and smooth
muscles e.g. gut muscle
☆skeletal (biceps)
☆multi nucleated
☆striated/stripped
☆long muscle fibers
☆block/cylindrical
☆smooth muscles
☆un nucleated
☆un striated
☆short muscle fibers
☆spindle shaped
ii) Name the cartilage found between the bones of the vertebral column
☆intervebral disc
iv) What are the functions of the cartilage named in (d) ii) above
☆acts as a cushion/absorbs shock
☆reduces friction
☆flexibility of vertebral column.
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